U.S. patent application number 13/104153 was filed with the patent office on 2012-11-15 for method and system for controlling engine vacuum production.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Ralph Wayne Cunningham, Ross Dykstra Pursifull.
Application Number | 20120285421 13/104153 |
Document ID | / |
Family ID | 47141002 |
Filed Date | 2012-11-15 |
United States Patent
Application |
20120285421 |
Kind Code |
A1 |
Cunningham; Ralph Wayne ; et
al. |
November 15, 2012 |
Method and System for Controlling Engine Vacuum Production
Abstract
A method for controlling engine vacuum production is disclosed.
In one example, one or more air sources to an engine intake
manifold are closed so as to increase an amount of air drawn from
another air source. The method may increase a rate of vacuum
supplied to a vacuum actuated device so as to improve operation of
the vacuum actuated device.
Inventors: |
Cunningham; Ralph Wayne;
(Milan, MI) ; Pursifull; Ross Dykstra; (Dearborn,
MI) |
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
Dearborn
MI
|
Family ID: |
47141002 |
Appl. No.: |
13/104153 |
Filed: |
May 10, 2011 |
Current U.S.
Class: |
123/436 |
Current CPC
Class: |
F02M 35/10222 20130101;
F02D 13/0265 20130101; Y02T 10/42 20130101; F02B 37/00 20130101;
B60T 17/02 20130101; F02D 41/0032 20130101; F02D 9/02 20130101;
F02M 35/10229 20130101; Y02T 10/40 20130101; F02D 41/0002 20130101;
F02D 41/04 20130101; F02D 2250/41 20130101 |
Class at
Publication: |
123/436 |
International
Class: |
F02M 7/00 20060101
F02M007/00 |
Claims
1. An engine operating method, comprising: closing air sources,
including a throttle, to an engine intake manifold in response to a
vacuum level; evacuating air from an air source supplying air to
the engine intake manifold that is not closed; and opening at least
one of the closed air sources in response to engine combustion
stability degrading below a threshold level.
2. The engine operating method of claim 1, where the air sources
include a fuel vapor purging system, and where the air source that
is not closed is a brake booster.
3. The engine operating method of claim 1, where the air sources
include an ejector.
4. The engine operating method of claim 1, where engine combustion
stability is estimated via an intake manifold pressure.
5. The engine operating method of claim 1, further comprising
adjusting engine spark advance in response to an intake manifold
pressure.
6. The engine operating method of claim 1, where closing of air
sources includes closing a group of air sources at substantially
the same time.
7. An engine operating method, comprising: closing air sources to
an engine intake manifold in a predetermined order in response to a
vacuum level, the air sources including a throttle; evacuating air
from an air source supplying air to the engine intake manifold that
is not closed; opening closed air sources in a predetermined order
in response to engine combustion stability degrading below a
threshold level.
8. The engine operating method of claim 7, where closing air
sources to the engine intake manifold in a predetermined order
includes closing a group of air sources at substantially a same
time.
9. The engine operating method of claim 7, where closing air
sources to the engine intake manifold in the predetermined order
includes beginning to close an engine air intake throttle before
other air sources.
10. The engine operating method of claim 7, where opening the
closed air sources in a predetermined order in response includes
beginning to open an engine air intake throttle before other air
sources.
11. The engine operating method of claim 10, further comprising
deactivating at least one engine cylinder while evacuating air from
the air source that is not closed.
12. The engine operating method of claim 10, further comprising
adjusting engine spark in response to engine intake manifold
pressure.
13. The engine operating method of claim 7, where the vacuum level
is predicted via an operating condition of a vehicle brake
actuator.
14. The engine operating method of claim 7, further comprising
opening the closed air sources in response to a vacuum level
greater than a threshold vacuum level.
15. The engine system, comprising: an engine with an intake
manifold and at least one cylinder; a plurality of air sources
providing air to the intake manifold, the plurality of air sources
including an engine air intake throttle; and a controller, the
controller including instructions for closing at least one of the
plurality of air sources in response to a vacuum level and for
opening the at least one of the plurality of air sources in
response to engine combustion stability degrading below a threshold
level.
16. The engine system of claim 15, where the controller includes
instructions for closing the engine air intake throttle in response
to the vacuum level.
17. The engine system of claim 15, further comprising a brake
booster, and where the vacuum level is a vacuum level of the brake
booster.
18. The engine system of claim 15, further comprising an ejector
and additional controller instructions to inhibit air flow to the
ejector in response to the vacuum level.
19. The engine system of claim 15, further comprising additional
controller instructions for opening a group of the plurality of air
sources in a predetermined order.
20. The engine system of claim 19, where the predetermined order
includes opening the engine air intake throttle before other air
sources in the group of the plurality of air sources.
Description
BACKGROUND/SUMMARY
[0001] Engine and vehicle actuators may be operated via vacuum or
electrical energy. Electrical energy may be suitable for operating
actuators that require a moderated amount of force; however, vacuum
may be more suitable for operating actuators that may require
higher levels of force such as vehicle brakes. Vacuum for operating
actuators may be supplied via an engine intake manifold or a vacuum
pump. An engine may provide vacuum via an intake manifold
positioned in the engine air intake path between engine cylinders
and an engine throttle. The pumping of engine cylinders may lower
pressure in the intake manifold with respect to atmospheric
pressure, thereby producing vacuum. However, engine air sources
supplying air to the engine may affect the way vacuum is produced
by the engine. For example, the engine throttle, engine crankcase
ventilation system, EGR, and fuel vapor control system may affect
the rate of vacuum production by the engine since the engine
throttle and fuel vapor control system supply air to the intake
manifold. In addition, the engine throttle and the fuel vapor
control system may affect the level of vacuum produced by the
engine. Further, choosing between liquid and gaseous fuels in a
bi-fuel engine can also affect engine vacuum production.
Consequently, if larger diameter hoses are used between vacuum
system components to improve vacuum recovery rate of a vacuum
system, the engine may not be able to provide vacuum at a desired
rate and level.
[0002] The inventors herein have recognized the above-mentioned
disadvantages and have developed an engine operating method,
comprising: closing air sources to an engine intake manifold in
response to a vacuum level, the air sources including a throttle;
evacuating air from an air source supplying air to the engine
intake manifold that is not closed; and opening at least one of the
closed air sources in response to engine combustion stability
degrading below a threshold level.
[0003] By restricting air flow or other gases flowing into the
engine via closing gas sources capable of providing gas to the
engine, the engine can be operated as a vacuum pump to quickly
resupply a vacuum system with vacuum. In one example, a throttle
supplying air to the engine may be closed in response to a brake
booster vacuum level. The throttle may be at least partially
reopened in response to a combustion stability level of the engine
so that the possibility of engine emission degradation may be
reduced during the vacuum recovery period.
[0004] The present description may provide several advantages. For
example, the approach may reduce the possibility of engine stalls
while increasing a rate of engine vacuum production. In addition,
some cylinders of a multi-cylinder engine may be operated without
fuel to produce vacuum while other cylinders operate with fuel to
produce engine torque. Further, the engine may provide higher
vacuum levels since the engine throttle can be closed during vacuum
production. Further still, engine air sources can be opened in a
predetermined order after being closed so as to prioritize
operation of vacuum consumers.
[0005] The above advantages and other advantages, and features of
the present description will be readily apparent from the following
Detailed Description when taken alone or in connection with the
accompanying drawings.
[0006] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE FIGURES
[0007] FIG. 1 shows a schematic depiction of an engine and vacuum
system;
[0008] FIGS. 2 and 3 show simulated signals of interest during an
engine operating sequence; and
[0009] FIG. 4 shows flowchart of an example method for controlling
engine vacuum production.
DETAILED DESCRIPTION
[0010] The present description is related to controlling production
of vacuum by an engine. In one example, the engine provides vacuum
to vacuum actuators of a vehicle. FIG. 1 shows one example of an
engine and vacuum system.
[0011] FIGS. 2-3 show simulated signals of interest while operating
an engine and producing vacuum for a vacuum system. During selected
engine operating conditions, air supplied via air sources can be
interrupted from reaching the engine intake manifold and cylinders.
Air supplied to the engine may be reinitiated when engine
combustion stability is less than a threshold level. As a result, a
vacuum level and rate of vacuum produced by the engine may be
increased while the possibility of engine stalling may be reduced.
FIG. 4 shows an example method for controlling air flow to the
engine.
[0012] Referring to FIG. 1, internal combustion engine 10,
comprising a plurality of cylinders, one cylinder of which is shown
in FIG. 1, is controlled by electronic engine controller 12. Engine
10 includes combustion chamber 30 and cylinder walls 32 with piston
36 positioned therein and connected to crankshaft 40. Combustion
chamber 30 is shown communicating with intake manifold 44 and
exhaust manifold 48 via respective intake valve 52 and exhaust
valve 54. Each intake and exhaust valve may be operated by an
intake cam 51 and an exhaust cam 53. Alternatively, one or more of
the intake and exhaust valves may be operated by an
electromechanically controlled valve coil and armature assembly.
The position of intake cam 51 may be determined by intake cam
sensor 55. The position of exhaust cam 53 may be determined by
exhaust cam sensor 57.
[0013] Fuel injector 66 is shown positioned to inject fuel directly
into cylinder 30, which is known to those skilled in the art as
direct injection. Alternatively, fuel may be injected to an intake
port, which is known to those skilled in the art as port injection.
Fuel injector 66 delivers liquid fuel in proportion to the pulse
width of signal FPW from controller 12. Fuel is delivered to fuel
injector 66 by a fuel system (not shown) including a fuel tank,
fuel pump, and fuel rail (not shown). Fuel injector 66 is supplied
operating current from driver 68 which responds to controller 12.
In addition, intake manifold 44 is shown communicating with
optional electronic throttle 62 which adjusts a position of
throttle plate 64 to control air flow from intake boost chamber 46.
Compressor 162 draws air from air intake 42 to supply boost chamber
46. Exhaust gases spin turbine 164 which is coupled to compressor
162 via shaft 161. A high pressure, dual stage, fuel system may be
used to generate higher fuel pressures at injectors 66. Intake
manifold 44 also provides vacuum to brake booster 140 via conduit
142. Check valve 144 ensures air flows from brake booster 140 to
intake manifold 44 and not from intake manifold 44 to brake booster
140. Brake booster 140 amplifies force provided by foot 152 via
brake pedal 150 to master cylinder 148 for applying vehicle brakes
(not shown). Ejector 20 may also supply vacuum to brake booster 140
via check valve 143. Check valve 143 ensures air flows from brake
booster 140 to ejector 20 and not from ejector 20 to brake booster
140. Ejector control valve 21 allows air to be directed from boost
chamber 46 through ejector 20 and to intake manifold 44 or air
intake 42 via check valves 145 and 141. In this way, air may be
directed to the lowest pressure area in the engine intake system
while ejector 20 is providing vacuum to the vacuum system.
[0014] A fuel vapor purging system comprising a fuel vapor canister
23 may hold stored fuel vapors from a fuel tank (not shown) or
other fuel vapor sources. Evaporative emission control valve 24
allows air from the atmosphere to be drawn into fuel vapor canister
23 and into intake manifold 44 when open. Thus, air can be supplied
to engine 10 when evaporative emission control valve 24 is open.
The state of evaporative emission control valve 24 is adjusted via
controller 12.
[0015] An engine crankcase ventilation system comprising an engine
crankcase 25 may hold crankcase gases. PCV control valve 26 allows
gases from the engine crankcase to be drawn into intake manifold 44
when open. Thus, crankcase gases can be supplied to engine 10 when
PCV control valve 24 is open. The state of PCV control valve 26 is
adjusted via controller 12.
[0016] HVAC actuators 28 can adjust heating and ventilation ducts
when HVAC control valve 27 is open allowing air to flow from HVAC
actuators 28. Thus, air can be supplied to engine 10 from HVAC
actuators 28 when HVAC control valve 24 is open. The state of HVAC
control valve 24 is adjusted via controller 12.
[0017] Distributorless ignition system 88 provides an ignition
spark to combustion chamber 30 via spark plug 92 in response to
controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126 is
shown coupled to exhaust manifold 48 upstream of catalytic
converter 70. Alternatively, a two-state exhaust gas oxygen sensor
may be substituted for UEGO sensor 126.
[0018] Converter 70 can include multiple catalyst bricks, in one
example. In another example, multiple emission control devices,
each with multiple bricks, can be used. Converter 70 can be a
three-way type catalyst in one example.
[0019] Controller 12 is shown in FIG. 1 as a conventional
microcomputer including: microprocessor unit 102, input/output
ports 104, read-only memory 106, random access memory 108, keep
alive memory 110, and a conventional data bus. Controller 12 is
shown receiving various signals from sensors coupled to engine 10,
in addition to those signals previously discussed, including:
engine coolant temperature (ECT) from temperature sensor 112
coupled to cooling sleeve 114; a position sensor 134 coupled to an
accelerator pedal 130 for sensing accelerator position adjusted by
foot 132; a position sensor 154 coupled to brake pedal 150 for
sensing brake pedal position, an optional pressure sensor 90 for
sensing cylinder pressure; a pressure sensor 146 for sensing brake
booster vacuum; a pressure sensor 147 for sensing master cylinder
pressure (e.g., hydraulic brake pressure); a knock sensor for
determining ignition of end gases (not shown); a measurement of
engine manifold pressure (MAP) from pressure sensor 122 coupled to
intake manifold 44; an engine position sensor from a Hall effect
sensor 118 sensing crankshaft 40 position; a measurement of air
mass entering the engine from sensor 120 (e.g., a hot wire air flow
meter); and a measurement of throttle position from sensor 58.
Barometric pressure may also be sensed (sensor not shown) for
processing by controller 12. In a preferred aspect of the present
description, engine position sensor 118 produces a predetermined
number of equally spaced pulses every revolution of the crankshaft
from which engine speed (RPM) can be determined.
[0020] In some embodiments, the engine may be coupled to an
electric motor/battery system in a hybrid vehicle. The hybrid
vehicle may have a parallel configuration, series configuration, or
variation or combinations thereof. Further, in some embodiments,
other engine configurations may be employed, for example a diesel
engine.
[0021] During operation, each cylinder within engine 10 typically
undergoes a four stroke cycle: the cycle includes the intake
stroke, compression stroke, expansion stroke, and exhaust stroke.
During the intake stroke, generally, the exhaust valve 54 closes
and intake valve 52 opens. Air is introduced into combustion
chamber 30 via intake manifold 44, and piston 36 moves to the
bottom of the cylinder so as to increase the volume within
combustion chamber 30. The position at which piston 36 is near the
bottom of the cylinder and at the end of its stroke (e.g. when
combustion chamber 30 is at its largest volume) is typically
referred to by those of skill in the art as bottom dead center
(BDC). During the compression stroke, intake valve 52 and exhaust
valve 54 are closed. Piston 36 moves toward the cylinder head so as
to compress the air within combustion chamber 30. The point at
which piston 36 is at the end of its stroke and closest to the
cylinder head (e.g. when combustion chamber 30 is at its smallest
volume) is typically referred to by those of skill in the art as
top dead center (TDC). In a process hereinafter referred to as
injection, fuel is introduced into the combustion chamber. In a
process hereinafter referred to as ignition, the injected fuel is
ignited by known ignition means such as spark plug 92, resulting in
combustion. During the expansion stroke, the expanding gases push
piston 36 back to BDC. Crankshaft 40 converts piston movement into
a rotational torque of the rotary shaft. Finally, during the
exhaust stroke, the exhaust valve 54 opens to release the combusted
air-fuel mixture to exhaust manifold 48 and the piston returns to
TDC. Note that the above is described merely as an example, and
that intake and exhaust valve opening and/or closing timings may
vary, such as to provide positive or negative valve overlap, late
intake valve closing, or various other examples.
[0022] Thus, the system of FIG. 1 provides for an engine with an
intake manifold and at least one cylinder; a plurality of air
sources providing air to the intake manifold, the plurality of air
sources including an engine air intake throttle; and a controller,
the controller including instructions for closing at least one of
the plurality of air sources in response to a vacuum level and for
opening the at least one of the plurality of air sources in
response to engine combustion stability degrading below a threshold
level. The engine controller also includes instructions for closing
the engine air intake throttle in response to the vacuum level. The
engine system further comprises a brake booster, and where the
vacuum level is a vacuum level of the brake booster. The engine
system further comprises an ejector and additional controller
instructions to inhibit air flow to the ejector in response to the
vacuum level. In another example, the engine system further
comprises additional controller instructions for opening a group of
the plurality of air sources in a predetermined order. The engine
system also includes where the predetermined order includes opening
the engine air intake throttle before other air sources in the
group of the plurality of air sources.
[0023] Referring now to FIGS. 2-3, simulated signals of interest
during an engine operating sequence are shown. The signals of FIG.
2 and FIG. 3 occur at the same time and during the same conditions.
Vertical markers T.sub.0-T.sub.11 identify particular times of
interest during the operating sequence and occur at the same time
between FIGS. 2 and 3. The signals of FIGS. 2 and 3 may be provided
via the system of FIG. 1 executing instructions according to the
method of FIG. 4.
[0024] The first plot from the top of FIG. 2 shows brake actuator
demand. The brake actuator demand may be made via a pedal as shown
in FIG. 1 or via a signal from a controller. Brake actuator demand
is at its lowest value at the bottom of the plot and increases in
magnitude toward the top of the plot and in the direction of the Y
axis arrow. The X axis represents time and time increases from the
left to the right side of the plot.
[0025] The second plot from the top of FIG. 2 shows brake booster
vacuum versus time. Time starts at the left side of the plot and
increases to the right. Brake booster vacuum is at its lowest value
at the bottom of the plot and increases toward the top of the plot
in the direction of the Y axis arrow. Horizontal marker 202
represents a brake booster threshold vacuum in the second plot. In
one example, one or more air sources supplying air to an engine are
closed when brake booster vacuum is less than threshold 202.
[0026] The third plot from the top of FIG. 2 shows engine throttle
position versus time (e.g. element 134 of FIG. 1). Time starts at
the left side of the plot and increases to the right. The throttle
opening increases in the direction of the Y axis arrow. The
throttle is closed near the bottom of the third plot.
[0027] The fourth plot from the top of FIG. 2 shows engine
combustion stability versus time. Time starts at the left side of
the plot and increases to the right. In one example, combustion
stability may be measured at a coefficient of variation of
indicated mean effective pressure IMEP. Combustion stability
increases in the direction of the Y axis arrow. Combustion
stability decreases in near the X axis. The horizontal line 204
represents a threshold combustion stability level.
[0028] The fifth plot from the top of FIG. 2 shows a position of a
normally open ejector control valve. The ejector control valve is
open and allows air flow to the engine when the signal is at a low
level. The ejector control valve is closed and inhibits air flow to
the engine when the signal is at a higher level.
[0029] The first plot from the top of FIG. 3 shows a position of a
normally open evaporative emission control valve. The evaporative
emission control valve is open and allows air flow to the engine
when the signal is at a low level. The evaporative emission control
valve is closed and inhibits air flow to the engine when the signal
is at a higher level.
[0030] The second plot from the top of FIG. 3 shows a position of a
normally open heating, ventilation, and air conditioning (HVAC)
control valve. The HVAC control valve is open and allows air flow
to the engine when the signal is at a low level. The HVAC control
valve is closed and inhibits air flow to the engine when the signal
is at a higher level.
[0031] At time T.sub.0, brake booster vacuum is at a relatively
high level and the brake actuator demand is at a low level. The
engine throttle position is also at a higher level indicating the
engine and vehicle equipped with the engine is operating at cruise
conditions. The combustion stability level is high indicating that
the engine is receiving an adequate engine air amount. The ejector,
evaporative emissions, and HVAC control valves are open indicating
that air may be drawn to the engine intake manifold when intake
manifold pressure is less than atmospheric pressure.
[0032] Shortly before time T.sub.1, the throttle position begins to
decrease and is indicative of a decreasing engine torque demand.
The brake actuator demand begins to increase at time T.sub.1 and is
indicative of application of vehicle brakes to slow the vehicle.
Applying the brake actuator causes air to enter the brake booster
and the vacuum level decreases accordingly. The engine combustion
stability remains at a higher level as air is available to engine
cylinders. The ejector, evaporative emissions, and HVAC control
valves remain open and allow air to flow to the engine.
[0033] At time T.sub.2, the brake actuator is partially released
allowing additional air to enter the brake booster. As a result,
the brake booster vacuum level decreases further to the level of
vacuum threshold 202. The engine throttle is closed in response to
the brake booster vacuum being less than a threshold level while
the engine torque demand is low. At the same time, the ejector,
evaporative emissions, and HVAC control valves are closed so at to
reduce the number of air sources delivering air to the engine. In
other examples, the ejector, evaporative emissions, and HVAC
control valves may be closed in a predetermined order based on
priority of vacuum use. In this way, air can be pumped from the
engine intake manifold at a higher rate than if all engine air
source were continuing to supply air to the engine. It should be
noted that not all engine air sources need be inhibited from
supplying air to the engine. In the example of FIG. 2, the brake
booster is an air source that remains in pneumatic communication
with the engine intake manifold. Therefore, the engine cylinders
can evacuate air from the engine intake manifold and the brake
booster while other air sources including the engine throttle are
substantially inhibited (e.g., some air flow may still pass by the
engine throttle even though the engine throttle is closed due to
clearances) from allowing air to flow to the engine. The engine
combustion stability remains at a higher level.
[0034] At time T.sub.3, the brake actuator demand increases again
and air flows to the brake booster. The air also flows to the
engine intake manifold since the brake booster remains in
communication with the intake manifold. The throttle remains closed
as do the ejector, evaporative emission, and HVAC control valves.
Engine cylinders evacuate air from the engine intake manifold and
the brake booster. After a short period of time, the brake booster
and engine intake manifold reach a higher level of vacuum and
engine combustion stability begins to degrade.
[0035] At time T.sub.4, the engine combustion stability has
degraded to a threshold level a 204. The engine throttle position
is increased so as to allow additional air to flow to engine
cylinders, thereby improving combustion stability. Further, a short
time after the engine throttle position is increased, the ejector,
evaporative emissions, and HVAC control valves are opened to allow
additional air to the engine and provide vacuum to the ejector,
evaporative emission system, and HVAC controls. The combustion
stability level increases after the engine throttle is partially
opened. The brake booster vacuum level remains at a high level and
increases slightly as the ejector increases the vacuum level
supplied to the brake booster. A check valve (e.g., 144 of FIG. 1)
allows the engine intake manifold pressure to increase while brake
booster vacuum level is maintained.
[0036] At time T.sub.5, the brake actuator demand is released
allowing air to flow into the brake booster. The vacuum in the
brake booster does not reach the vacuum threshold 202. Therefore,
the engine throttle, ejector control valve, evaporative emissions
control valve, and the HVAC control valves remain open. The engine
combustion stability also remains above combustion stability
threshold 204.
[0037] Between time T.sub.5 and time T.sub.6, the engine throttle
position increases as is indicative of vehicle acceleration. The
engine combustion stability remains at a higher level and the
engine air sources are in pneumatic communication with the engine
intake manifold. Further, the brake booster vacuum level increases
as vacuum is supplied to the brake booster via the ejector. The
brake actuator demand remains inactive. The engine throttle
partially closes to a level where air to idle the engine during
warm operating conditions is delivered.
[0038] At time T.sub.6, the brake actuator demand increases as is
indicative of a request to slow a vehicle. The brake booster vacuum
level decreases as air flows into the brake booster via applying
the brake actuator. The engine combustion stability remains at a
higher level and the ejector, evaporative emissions, and HVAC
control valves remain open allowing air to flow to the engine via
engine air sources.
[0039] Between time T.sub.6 and time T.sub.7, the brake actuator
demand slowly increases allowing additional air to enter the brake
booster. Accordingly, the brake booster vacuum continues to
decrease.
[0040] At time T.sub.7, the brake booster vacuum reaches threshold
level 202. The engine throttle is closed so that engine cylinders
pump air from the engine intake manifold and brake booster at an
increased rate. Similarly, the ejector, evaporative emissions, and
HVAC control valves are closed to increase the rate air is pumped
from the engine intake manifold and brake booster.
[0041] At time T.sub.8, the engine combustion stability degrades to
threshold level 204. Consequently, the engine throttle is partially
opened to allow additional air to engine cylinders. Further, the
ejector, evaporative emissions, and HVAC control valves are
commanded open in a predetermined order. The ejector control valve
is opened followed by the evaporative emissions control valve and
then by the HVAC control valve. The engine combustion stability
increases shortly thereafter. However, in other examples priority
to vacuum consumers may be in a different order. Further, in some
examples, different vacuum consumers may be reactivated at
different levels of vacuum within the system. For example, vacuum
consumers may be reactivated or pneumatically coupled to a vacuum
reservoir with each 0.1 bar decrease in vacuum after the combustion
stability threshold has been reached.
[0042] At time T.sub.9, the brake actuator demand is reduced
allowing air to flow into the brake booster. Since the ejector has
been activated by putting the ejector in pneumatic communication
with the engine intake manifold, the ejector provides vacuum to the
vacuum system. The throttle remains partially open supplying an
engine idle air amount to engine cylinders. The ejector,
evaporative emissions, and HVAC control valves remain open since
the brake booster vacuum level is higher than vacuum threshold
202.
[0043] Between time T.sub.9 and time T.sub.10, the throttle
position is increased and decreased as indicative of vehicle
acceleration. The brake booster vacuum level stays high as no
vacuum is consumed via brake actuator demand. The engine combustion
stability level also remains at a higher level as there is adequate
air supply to the engine cylinders.
[0044] At time T.sub.10, the brake actuator demand is increased as
is indicative of a request to slow a vehicle down. Air flows into
the brake booster when the brake actuator is applied and so the
brake booster vacuum level decreases. Since the ejector is active,
additional vacuum may be provided via the ejector. In addition,
additional vacuum may be provided to the brake booster via the
engine intake manifold. The ejector, evaporative emissions, and
HVAC control valves remain open since the brake booster vacuum
level remains relatively high.
[0045] At time T.sub.11, the brake actuator demand begins to slowly
decrease as is indicative of slowly releasing a vehicle brake
pedal. As a result, air enters the brake booster and slowly
decreases the brake booster vacuum level. The engine throttle
remains at a level where the engine and idle during warm engine
operating conditions.
[0046] At time T.sub.12, the brake booster vacuum level decreases
to a level below the threshold level. Consequently, the engine
throttle is closed and the ejector, evaporative emissions, and HVAC
control valves are also close to increase the rate vacuum is
provided to the brake booster. It should be noted that a vacuum
reservoir or canister vacuum level may be monitored and the basis
for stopping air flowing into the engine from engine air sources
rather than the brake booster, if desired.
[0047] Referring now to FIG. 4, a flowchart of an example method
for controlling engine vacuum production is shown. The method of
FIG. 4 may be executed via controller instructions via the system
of FIG. 1.
[0048] At 402, method 400 determines engine operating conditions.
Engine operating conditions may include but are not limited to
engine speed, engine cylinder air amount, ambient temperature and
pressure, system vacuum levels, cylinder pressure, and throttle
position. Method 400 proceeds to 404 after engine operating
conditions are determined.
[0049] At 404, method 400 judges whether or not a vacuum level in
the vehicle vacuum system is less than a threshold vacuum level and
if a desired engine torque level is available from engine air
sources other than the throttle (e.g., air presently in the intake
manifold, brake booster air, vacuum reservoir air, evaporative
emissions air, HV AC system air, or positive crankcase ventilation
air). If so, method 400 proceeds to 406. Otherwise, method 400
proceeds to 424.
[0050] At 406, the engine throttle controlling air flow from the
engine air intake to engine cylinders is closed. The engine
throttle may be fully closed or partially closed. In examples,
where the engine throttle is mechanically controlled, or where a
bypass valve can route air around the throttle, the bypass valve
may be closed. Method 400 proceeds to 408 after the throttle is
closed.
[0051] At 408, method 400 closes the evaporative emissions control
valve (e.g., 24 in FIG. 1). Closing the evaporative emissions
control valve prevents air from flowing through an evaporative
emissions canister and into the engine intake manifold. And, since
the evaporative emissions control valve is in pneumatic
communication with the engine intake manifold, loss of engine
intake manifold vacuum may be prevented by closing the evaporative
emissions control valve. Method 400 proceeds to 410 after the
evaporative emission control valve is closed.
[0052] At 410, a HVAC control valve (e.g., 27 of FIG. 1) and/or
other vacuum consumer control valves (e.g., PCV valve) may be
closed. Closing the HVAC control valve prevents air from flowing
through the HVAC actuator and into the engine intake manifold. And,
since the HVAC control valve is in pneumatic communication with the
engine intake manifold, loss of engine intake manifold vacuum may
be prevented by closing the HVAC control valve. Method 400 proceeds
to 412 after the HVAC control valve is closed.
[0053] At 412, method 400 closes an ejector control valve (e.g., 21
in FIG. 1). The ejector control valve is closed last after other
engine air sources when production of additional vacuum is
requested. The ejector control valve is closed last so that vacuum
can be supplied by the ejector for a longer period of time. Closing
the ejector control valve prevents air from flowing through the
ejector. Vacuum may be produced by the ejector where air passes
through the ejector. Thus, vacuum production by the ejector can be
prevented by closing the ejector control valve. In addition, since
the ejector is pneumatically coupled to the engine intake manifold,
loss of engine intake manifold vacuum may be prevented by closing
the ejector control valve. Method 400 proceeds to 414 after closing
the ejector control valve.
[0054] From 406 to 412 engine air sources are inhibited from
communicating with the engine intake manifold. The engine air
sources may limit communication with the engine intake manifold in
a predetermined order or substantially simultaneously. For example,
when there is an operator torque request between a first and second
threshold levels, the ejector, evaporative emissions, and HVAC
control valves can be closed before the throttle so that the
throttle can respond to operator input. In another example, where
there is no operator torque request, the throttle can be closed
before the evaporative emissions, HVAC, and ejector control valves.
In other examples, the order in which the ejector, evaporative
emissions, and HVAC control valves are closed may be varied
depending on the amount of fuel vapors stored. For example, if a
higher amount of fuel vapors are stored, the evaporative emissions
control valve may be closed last, after the HVAC and ejector
control valves, so that additional fuel vapors may be purged. In
addition, engine air source control valves can be closed in
response to vacuum levels in the vacuum system. For example, the
evaporative emissions control valve may be closed when vacuum is at
a first vacuum level. The ejector control valve may be closed when
the vacuum is at a second level, the second level a higher vacuum
level than the first vacuum level. Since different vacuum levels
occur at different times, one valve may open at a later time than
one or more of the other valves. In this way, priority may be
provided to removing selected vacuum consumers from the vacuum
system. Further, only a subset of engine air sources from 406 to
412 may be closed to increase vacuum production, if desired.
[0055] Engine spark may also be adjusted as engine air sources are
closed and air from the closed engine air sources is prevented from
entering the engine. In one example, spark may be advanced as
engine air sources are closed. In other examples, engine spark
advance may continue to be adjusted according to engine speed and
intake manifold pressure.
[0056] It should also be mentioned that one or more cylinders may
be deactivated by ceasing fuel delivery to the cylinder and/or
closing cylinder intake valves. If engine cylinders are deactivated
via closing intake valves, more air may be made available to active
cylinders so that engine cylinder combustion stability may be at a
higher level for a longer period of time.
[0057] At 414, method 400 judges whether or not engine combustion
stability is less than an engine threshold combustion stability
level or if the engine torque request requires more air than is
available from air sources that have not been stopped from
supplying air to the engine cylinders (e.g., the engine intake
manifold and vacuum system vacuum reservoirs such as the brake
booster). If so, method 400 proceeds to 416. Otherwise, method 400
returns to 414 until combustion stability degrades to a threshold
level or until increased engine torque is requested.
[0058] At 416, method 400 at least partially opens the engine
throttle. If the engine torque request has increased, the engine
throttle position is adjusted to a level where the desired engine
torque may be provided. If engine combustion stability has degraded
to a threshold level, the engine throttle is opened to an amount
where engine combustion stability is improved to a level greater
than a threshold level. In examples where a bypass air valve around
the engine throttle is present, the bypass valve may be opened.
[0059] At 418, method 400 opens the ejector control valve. Opening
the ejector control valve allows additional air to flow to the
engine and also allows for the generation of vacuum so that the
vacuum level in the vacuum system may be increased. The ejector
valve may be fully or partially opened in response to engine
combustion stability degradation. Method 400 proceeds to 420 after
the ejector control valve is opened.
[0060] At 420, method 400 opens the evaporative emissions control
valve. Similar to the ejector control valve, opening the
evaporative emissions control valve allows additional air to flow
to the engine. Opening the evaporative emission control valve also
allows for stored fuel vapors to be purged from the fuel system and
combusted by the engine. The evaporative emissions control valve
may be fully or partially opened in response to engine combustion
stability degradation. Method 400 proceeds to 422 after the
evaporative emissions control valve is opened.
[0061] At 422, method 400 opens the HVAC and/or other vacuum
consumer control valves. HVAC system ducts may be controlled when
air is allowed to flow from HVAC actuators to the engine intake
manifold. The HVAC control valve may be fully or partially opened
in response to engine combustion stability degradation. Method 400
proceeds to exit after the HVAC control valve is opened.
[0062] From 416 to 422 engine air sources are put in communication
with the engine intake manifold. The engine air sources may
establish communication with the engine intake manifold in a
predetermined order or substantially simultaneously. For example,
when there is an operator torque request the throttle may be opened
before the ejector, evaporative emissions, and HVAC control valves.
However, if there is no operator torque demand, the ejector control
valve may be opened followed by the evaporative emissions control
valve and then by the HVAC control valve. In other examples, the
order in which the ejector, evaporative emissions, and HVAC control
valves are opened may be varied depending on the amount of fuel
vapors stored. For example, if a higher amount of fuel vapors are
stored, the evaporative emissions control valve may be opened first
so that additional fuel vapors may be purged. However, if the
amount of fuel vapors stored is low, the ejector control valve may
be opened first to provide additional vacuum. In addition, engine
air source control valves can be opened in response to vacuum
levels in the vacuum system. For example, the ejector may be opened
when vacuum is at a first vacuum level. The evaporative emissions
control valve may be opened when the vacuum is at a second level,
the second level a higher vacuum level than the first vacuum level.
In this way, priority may be provided to removing selected vacuum
consumers from the vacuum system. In one example, where combustion
stability is initially degraded, the engine throttle is opened at
416 when the desired engine air flow is less than a threshold and
other vacuum consumers 418 to 422 remain closed so as to provide a
higher vacuum level while improving combustion stability. In this
way, the throttle may make fine adjustments to engine air flow to
increase combustion stability while increasing vacuum production
for the vacuum system.
[0063] At 424, method 400 produces vacuum for the brake booster and
vacuum system vacuum reservoirs. Vacuum may be provided via the
engine intake manifold when the engine throttle is partially
closed. Check valves in the vacuum system (e.g., 143 and 144 of
FIG. 1) may limit the direction of air flow in the vacuum system so
as to ensure that the vacuum system reservoirs are at high vacuum
levels when possible. Since the engine responds to operator torque
requests it may be difficult at times for the engine to provide
vacuum when desired. Method 400 proceeds to 426 after attempting to
produce vacuum via the engine.
[0064] At 426, method 400 produces vacuum for the vehicle vacuum
system via an ejector (e.g., 20 of FIG. 1). The ejector may provide
vacuum when air passes through the ejector. Air passing through the
ejector produces a low pressure region in the ejector allowing air
from the vacuum system to be drawn to the ejector and evacuated
from the vacuum system. Method 400 proceeds to exit after producing
vacuum for the vacuum system via the ejector.
[0065] Thus, the method of FIG. 4 provides for an engine operating
method, comprising: closing air sources, including a throttle, to
an engine intake manifold in response to a vacuum level; evacuating
air from an air source supplying air to the engine intake manifold
that is not closed; and opening at least one of the closed air
sources in response to engine combustion stability degrading below
a threshold level. The engine operating method also includes where
the air sources include a fuel vapor purging system, and where the
air source that is not closed is a brake booster. In one example,
the engine operating method includes where the air sources is an
ejector. Further, according to the method, engine combustion
stability is estimated via an intake manifold pressure or cylinder
pressure. The engine operating method further comprises adjusting
engine spark advance in response to an intake manifold pressure.
The engine operating method also includes where closing of air
sources includes closing a group of air sources at substantially
the same time.
[0066] The method of FIG. 4 also provides for an engine operating
method, comprising: closing air sources to an engine intake
manifold in a predetermined order in response to a vacuum level,
the air sources including a throttle; evacuating air from an air
source supplying air to the engine intake manifold that is not
closed; opening closed air sources in a predetermined order in
response to engine combustion stability degrading below a threshold
level. The engine operating method also includes where closing air
sources to the engine intake manifold in a predetermined order
includes closing a group of air sources at substantially a same
time. The engine operating method also includes where closing air
sources to the engine intake manifold in the predetermined order
includes beginning to close an engine air intake throttle before
other air sources. The engine operating method also includes where
opening the closed air sources in a predetermined order in response
includes beginning to open an engine air intake throttle before
other air sources. In this way, a desired engine torque may be
provided rapidly. The engine operating method further comprises
deactivating at least one engine cylinder while evacuating air from
the air source that is not closed. The engine operating method also
includes where the vacuum level is predicted via an operating
condition of a vehicle brake actuator. In another example, the
engine operating method further comprises opening the closed air
sources in response to a vacuum level greater than a threshold
vacuum level.
[0067] As will be appreciated by one of ordinary skill in the art,
the method described in FIG. 4 may represent one or more of any
number of processing strategies such as event-driven,
interrupt-driven, multi-tasking, multi-threading, and the like. As
such, various steps or functions illustrated may be performed in
the sequence illustrated, in parallel, or in some cases omitted.
Likewise, the order of processing is not necessarily required to
achieve the objects, features, and advantages described herein, but
is provided for ease of illustration and description. Although not
explicitly illustrated, one of ordinary skill in the art will
recognize that one or more of the illustrated steps or functions
may be repeatedly performed depending on the particular strategy
being used.
[0068] This concludes the description. The reading of it by those
skilled in the art would bring to mind many alterations and
modifications without departing from the spirit and the scope of
the description. For example, single cylinder, I2, I3, I4, I5, V6,
V8, V10, V12 and V16 engines operating in natural gas, gasoline,
diesel, or alternative fuel configurations could use the present
description to advantage.
* * * * *